A CFT truss girder is a girder constructed by concrete filled steel tubes (CFTs), each being prepared by filling concrete in a steel tube, in a truss structure. An incremental launching method (hereinafter, referred to as “ILM”) has been used for constructing a bridge. In the ILM, a plurality of segment units, which will configure a superstructure of a bridge, is pre-fabricated at a casting bed built at the rear of an abutment, and then the segment units are pushed in a bridge axis direction in order by using an extrusion device such as a jack device to construct a bridge.
When constructing a bridge using the CFT truss girder and the concrete slab, it is desirable to use the ILM. However, an existing ILM has following problems, and these problems should be solved.
When a superstructure of a bridge, composed of a steel girder and a precast concrete slab, is constructed by means of an existing ILM, a unit of a superstructure should be completely pre-fabricated with a steel girder and an in-situ concrete slab before launching the unit. Thus, the existing technique has a drawback in an extended construction period. In addition, in the existing technique, while units of the superstructure are being launched in sequence, in order to offset a tensile stress applied to the concrete slab, a prestressing force should be continuously introduced to the concrete slab throughout the launching process. Thus, construction costs may be increased.
In the existing ILM, a steel girder may be launched in advance. However, in this case, a concrete slab should be fabricated with the steel girder by placing concrete in-site, and thus the extended construction period is not shortened. In addition, after the steel girder is launched, when the concrete slab is fabricated with the steel girder by placing concrete in-site, the fabrication work should be performed at a high place, which deteriorates construction efficiency and safety. Therefore, in order to construct a bridge having a superstructure bridge with a CFT truss girder and a concrete slab by means of the ILM, it is needed to solve the problems of the existing ILM as mentioned in the above.